The present invention relates to a method and an apparatus for producing a tubular container. By tubular container it is meant a continuous walled container which has a cross-section taken through the wall of the container being substantially arbitrary e.g. circular, elliptical polygonal, having at least one corner, one flat surface, etc. A round, oval or polysided container form embodiments of the invented container.
The present invention relates to a method and an apparatus for producing a tubular container according to the preambles to the respective independent claims. By tubular container it is meant a continuous walled container which has a cross-section taken through the wall of the container being substantially arbitrary e.g. circular, elliptical polygonal, having at least one corner, one flat surface, an inwardly curved surface etc. A round, oval or polysided container form embodiments of the invented container.
In the injection moulding of tubular containers of plastic material, the maximum length which can be obtained for the tubular portion of the container is determined by the selected material and the wall thickness of the tubular portion. In addition, the wall thickness may not be less than approx. 0.5 mm irrespective of the plastic material employed in the injection moulding. This relationship is clarified further later in the body of this description.
In the injection moulding of containers, the flow length of the supplied molten plastic material and, thereby, the unit formed in the injection moulding process is maximized by the material thickness. In purely practical terms, it has proved that injection moulded products having a wall thickness of less than 0.5 mm cannot be produced in mass production lines. Cf., for example, the book by Menges/Mohren, xe2x80x9cHow to Make Injection Moldsxe2x80x9d, 1986, Hanser Publishers (ISBN 0-19-520744-0 Oxford University Press), p. 66.
Tubular containers of plastic material have recently been adopted for use as tubes for, for example, toothpaste, handcreams etc. However, for the reasons outlined above it has been necessary to select material thicknesses for the tubular portion to be unnecessarily large or, otherwise it has been necessary to restrict the length of the tubular portion.
The present invention realizes a considerable materials saving, with the result that the costs involved in producing such containers are drastically reduced as compared with that which applies to tubular containers produced according the prior art technique. Cost savings of the order of magnitude of 40% have been achieved.
Expedient embodiments of the present invention are defined below in the appended subclaims.